Tunisia's moderate Islamist party was preparing to lead a coalition government today after its election win sent a message to the region that once-banned Islamists are challenging for power after the "Arab Spring".

With election officials still counting the ballot papers, the Ennahda party said its own, unofficial tally showed it had won Sunday's vote, the first since the uprisings which began in Tunisia and spread through the region.

Seeking to reassure secularists in Tunisia and elsewhere who see a threat to their liberal, modernist values, party officials said they would bring two secularist parties into a broad interim coalition that will govern the country.

"This is an historic moment," said Zeinab Omri, a young woman in a hijab, or Islamic head scarf, who was among a cheering crowd outside the Ennahda headquarters when party officials claimed victory late yesterday.

"No one can doubt this result. This result shows very clearly that the Tunisian people is a people attached to its Islamic identity," she said.

Two days after an unprecedented 90 per cent of voters turned out for the election, officials were still counting the ballot papers in some areas. They said nationwide results would not be ready before this afternoon.

Sunday's vote was for an assembly which will sit for one year to draft a new constitution. It will also appoint a new interim president and government to run the country until fresh elections late next year or early in 2013.

The voting system has built-in checks and balances which make it nearly impossible for any one party to have a majority, compelling Ennahda to seek alliances with secularist parties, which will dilute its influence.

Moncef Marzouki, the former dissident whose secularist Congress for the Republic was in second place according to unofficial results, said he was ready to work with Ennahda and with other parties.

"I am for a coalition government," Marzouki, who spent years in exile in France before Tunisia's revolution in January, told Reuters in an interview. "We wish to have a national government as wide as possible with all the parties."

"There are lots of challenges which await us, and the political class should be worthy of the Tunisian people, which has given an exceptional lesson for the world."

Ennahda officials named Marzouki's party, and the left-wing secularist Ettakatol party, as favoured coalition partners. Their presence in a coalition government may help reassure Tunisia's jittery secularists.

The election result is likely to resonate in Egypt, which starts voting in November in a multi-stage election. An Islamist party which shares much of the same ideology as Ennahda is predicted to perform strongly.

Tunisia became the birthplace of the "Arab Spring" when Mohamed Bouazizi, a vegetable seller in a provincial town, set fire to himself in protest at poverty and government repression.

His suicide in December provoked a wave of protests which forced autocratic President Zine al-Abidine Ben Ali to flee to Saudi Arabia the following month.

The revolution in Tunisia, a former French colony, in turn inspired uprisings which forced out entrenched leaders in Egypt and Libya, and convulsed Yemen and Syria - re-shaping the political landscape of the Middle East.

Ennahda is led by Rachid Ghannouchi, forced into exile in Britain for 22 years because of harassment by Ben Ali's police. A softly spoken scholar, he dresses in suits and open-necked shirts while his wife and daughter wear the hijab.

Ghannouchi is at pains to stress his party will not enforce any code of morality on Tunisian society, or the millions of Western tourists who holiday on its beaches. He models his approach on the moderate Islamism of Turkish Prime Minister Tayyip Erdogan.

The party's rise has been met with ambivalence by some people in Tunisia. The country's strong secularist traditions go back to the first post-independence president, Habiba Bourguiba, who called the hijab an "odious rag".

"I really feel a lot of fear and concern after this result," said Meriam Othmani, a 28-year-old journalist. "Women's rights will be eroded," she said. "Also, you'll see the return of dictatorship once Ennahda achieves a majority in the constituent assembly."

The highest-profile secularist challenger to Ennahda, the Progressive Democratic Party (PDP) conceded defeat. It had warned voters that modern, liberal values would be threatened if the Islamists won.

"We congratulate the winner and we will be in the ranks of the opposition," a party statement said.

Ennahda's win was a remarkable turnaround for a party which just 10 months ago had to operate underground because of a government ban which had put hundreds of followers in prison.

In a slick and well-funded campaign, the party tapped into a desire among ordinary Tunisians to be able to express their faith freely after years of aggressively enforced secularism.

Western diplomats say Ennahda is largely funded by Tunisian businessmen, which they say means the party will pursue pro-market economic policies.

It also sought to show it could represent all Tunisians, including the large number who take a laissez-faire view of Islam's strictures, drink alcohol, wear revealing clothes and rarely visit the mosque.

Secularist opponents say they believe this is just a cleverly constructed front that conceals more radical views, especially among Ennahda's rank and file in the provinces.